The Memotech Node Ring Network

The Cambridge Ring was an experimental Local Area Network (LAN), developed at the Computer Laboratory, University of Cambridge in the 1970's and 80's. It was a ring network that allowed the transmission of packets of data between the nodes in the ring over predominantly twisted pair cables.

The Cambridge Ring was capable of operating at 10 megabits/second using powerful hardware far beyond the capabilities of the Memotech MTX. The Internet Archive Wayback Machine has archived an article by David Greaves from 1999 which describes the Cambridge hardware.

Inspired by the Cambridge Ring, Robert Branton led the development of a token ring network for the Memotech MTX, which, although designed at the Memotech facilities in Witney, was originally called the Oxford Ring. The name appears to have been changed to the Memotech Ring by the time that the Operator's Manual was published.

Branton led a small team, including Tony Brewer, that developed the Memotech implementation designed to run on the MTX with no additional hardware, other than the ROM pak containing the firmware. According to Tony¹, "The work was complicated and took several months. The Zilog in-circuit emulator (ICE) was essential. We managed to complete the work just before the somewhat temperamental ICE stopped working for good."

Using the available MTX RS232 communications hardware, the ring communication mechanism used single-core coaxial cable at a rate of 19,200 bits per second, according to the manual, equivalent to a maximum data rate of about 30,000 bytes per minute. As noted by Tony¹, "The Ring was not super fast but it worked well." By way of comparison, an unmodified Commodore 64 disk drive transfer rate was about 300 bytes/second or 18,000 bytes per minute - i.e.., Node was almost twice as fast!

Tony also notes that "When finished we did a demo involving 12-16 MTX's in one large room at Witney. It was shown to one of Memotech's investors and the local MP (Douglas Hurd), possibly the USA rep as well."

It is likely that the intended market for the networking capabilities was education/schools, but sadly the MTX lost out to competing hardware, particularly the BBC Micro.

Some notes on the Memotech Ring connections can be found on this page.

Some notes on the Node variables and Ring packet structure can be found in the Technical Note created by Bill Brendling available on the Manuals page.

References :

1. E-mail discussion with Tony Brewer, October 2025